He added: "Willie Walsh can clearly see the opportunities of independence. A boost to tourism and travel in Scotland will have a positive impact on growth.

"Mr Walsh's comments further underline the UK government's duty to engage properly with the issues of the independence debate.

"Instead, the self-styled 'Project Fear' are intent on wasting time engaging in their 'dambuster' strategy of scaremongering and attempting to bully people in Scotland to vote 'No'."

Scottish tourism

However, the pro-Union Better Together campaign said APD was not the "strongest argument" for independence, and that jobs would be lost if Scotland voted "Yes".

A spokesman said: "Breaking up the most successful economic, political and social union in history for the sake of a tax on holidays doesn't seem like the strongest argument.

"As the intervention from Standard Life made abundantly clear, leaving the UK would cost jobs here in Scotland.

"Alex Salmond's failure to tell us what will replace the pound means companies like Standard Life and RBS, which employ thousands of people in Scotland, have warned about the big risks involved in going it alone."

Speaking on BBC Radio Scotland's Newsdrive programme, Michael O'Leary, chief executive of Ryanair, said he supported the position of the Scottish government in relation to the abolition of APD which he said "has done untold damage to Scottish tourism and particularly to traffic on domestic routes to and from Scotland".

He added: "It's not a narrow or small issue. Traffic in Scotland has declined in the past five years since travel tax has been imposed."

But Mr O'Leary said he didn't want to get involved in the debate about Scottish independence.

He said: "Speaking as an Irishman, that's a matter for the Scottish people. But certainly, if the air travel tax were repealed by the UK government or an independent Scottish government, you'd see visitors to Scotland double over a five to ten year period."

Contingency planning

Elsewhere, the body which represents engineering firms in Scotland has told the BBC that its members have "major concerns" about the impact of independence.

Engineering Scotland chief executive Bryan Buchan said the currency, tax rates and EU membership were the main areas of concern.

He said some big firms had drawing up contingency plans, although none had threatened to move operations from Scotland to England.

"We are seeing activity and we are, as a body, participating in assisting companies [with] contingency planning, particularly those which are foreign owned, where the parent is seeking to establish the landscape the business is operating in," he added.

A Scottish government spokesman insisted Scotland would keep the pound after independence, as part of a formal currency union.

He added: "An independent Scotland will continue in EU membership, and the only threat to that is Westminster's proposed in/out referendum which risks taking Scotland out of the EU against its will, with huge consequences for jobs, investment and prosperity."